Apparatus for establishing plasma boundary surfaces



M. HOFF Dec. 21, 1965 APPARATUS FOR ESTABLISHING PLASMA BOUNDARY SURFACES Filed Oct. 11, 1962 I megi I n V It I. r

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PSWER SUPPLY United States Patent Office 3,224,375 Patented Dec. 21, 1965 3,224,375 APPARATUS FOR ESTABLISHING PLASMA BOUNDARY SURFACES Marc Hoff, 12 Wren Drive, Woodbury, NY. Filed Oct. 11, 1962, Ser. No. 229,874 8 Claims. (Cl. 10292.5)

This invention relates to apparatus for establishing plasma boundary surfaces. It is particularly useful in repelling the plasma sheath which forms around the nose cone of a space missile upon reentry into the atmosphere and to contain the high-temperature plasma formed by atomic fusion in a thermonuclear reactor.

It is well known that in the operation of space missiles, there is a serious heating problem encountered upon atmospheric reentry, such heating ordinarily being effective to raise the temperature of the nose cone to the melting point or even to the vaporization point. It is believed that such intense heating can be explained, at least in part, by the fact that the air at the front end of the missile is ionized, absorbing energy from the kinetic energy of the missile. As the ionized air or plasma sweeps past the sides of the nose cone, it returns to its neutral or deionized state, liberating heat which is conducted to the metallic surface of the nose cone, raising its temperature as described.

One embodiment of the present invention is based upon the discovery that if the ionized plasma forming at the tip of the nose cone is deflected away from its side walls, the intense heating during the relatively short-duration reentry interval is reduced to a tolerable level and the further discovery that such plasma deflection may be effected by a relatively simple low-weight electromagnetic apparatus.

A further embodiment of the invention is based on the discovery that electromagnetic apparatus suitable for deflecting plasma from a missile nose cone, with slight modification, is effective to contain the high-temperature plasma formed by atomic fusion in a thermonuclear reactor.

It is an object of the invention therefore, to provide a new and improved apparatus for establishing plasma boundary surfaces which is effective, when applied to a space missile, to deflect ionized plasma, formed upon atmospheric reentry, away from the missile body, thereby substantially to reduce the heating thereof.

It is another object of the invention to provide a new and improved apparatus for establishing plasma boundary surfaces which is effective, when applied to a thermonuclear reactor, to contain the high-temperature plasma formed by atomic fusion and thus protect the walls of the reactor container from the high temperature of the plasma.

In accordance with the invention, there is provided a space missile reentry cone comprising a nonmagnetic metallic casing, 21 plasma-deflecting apparatus disposed within the casing and including a single-helix first electrical winding, a double-helix second electrical winding coaxial with said first winding, such first and second windings extending substantially the length of the casing, and circuit means for supplying current continuously to both of the windings, the ampere-turns of the two windings being proportioned to develop a peripheral magnetic field at least of the same order of intensity as their resultant axial field. The term helix" is used herein and in the appended claims to refer to a generally helical configuration of either uniform or tapered pitch.

For a better understanding of the present invention, together with other and further objects thereof, reference is had to the following description, taken in connection with the accompanying drawing, while its scope will be pointed out in the appended claims.

yield approximately fourteen turns.

Referring now to the drawing:

FIG. 1 is a longitudinal view, partly in section and partly schematic, of an apparatus for establishing plasma boundary surfaces applied to the nose cone of a space missile; while FIG. 2 is a longitudinal view, partly in section and partly schematic, of an apparatus for establishing plasma boundary surfaces applied to a thermonuclear reactor.

Referring now specifically to FIG. 1 of the drawing, there is represented the embodiment of an apparatus for establishing a plasma boundary in accordance with the invention in a space missile reentry cone. The apparatus comprises a casing 10 of nonmagnetic material, such as aluminum, having a forward end 10a of reduced crosssection, preferably approximating a needle point, and constructed of a material which is relatively readily vaporizable. By way of example, the point 10a may also be of aluminum.

A plasma deflecting apparatus is disposed within the casing 10 and includes a single-helix first electrical winding 11 having a pitch which progressively decreases toward the forward end of the cone. The apparatus further includes a double-helix second electrical winding 12 coaxial with the winding 11 and, as shown, electrically connected in series therewith to a power supply unit 13 which may be a battery, a bank of solar cells, or the like, through a switch 9. A capacitor 8 of large value may, if desired, be connected across the power supply 13 to develop a large momentary surge of current upon closing switch 9. Preferably, and as specifically illustrated, the winding 11, which may be termed the primary helical winding, has wound on it the double-helical winding 12, which may be termed the secondary helical winding. The circuit connections from the power supply 13 to the windings 11 and 12, in relation to their winding direction, is such that the polarities of the axial components of the magnetic fields of the windings 11 and 12 are opposed. Preferably, a layer of insulation material 14, such as glass wool, is interposed between the windings and the casing 10, it being understood, of course, that the windings 11 and 12 are insulated from each other as by constructing one or both of insulated wire.

In order to produce magnetic plasma deflecting fields of appropriate configuration, as discussed hereinafter, the ampere-turns of the windings 11 and 12 are proportioned to develop a peripheral magnetic field, that is. a magnetic field between adjacent turns, at least of the same order of intensity as the resultant axial field of the two windings. This characteristic is due in part to the fact that the axial components of the magnetic fields of the windings 11 and 12 are opposed, as the axial component of the field of the winding 12 alone is greatly in excess of its turn-to-turn peripheral field. For clarity of illustration, the turn-to-turn peripheral magnetic field of only the primary winding 11 is shown in FIG. 1 of the drawing. However, it will be obvious that the secondary winding 12 will develop a similar turn-to-turn peripheral magnetic field. It is well known that it is only the component of the magnetic field normal to the surface facing an ionized plasma that is effective in deflecting the plasma flowing past the surface. For clarity of illustration also, the relative spacings of the turns of the primary winding 11 have been shown greatly exaggerated. As pointed out hereinafter, in one embodiment in which the length of the shell was one and three-quarter inches, the pitch of the primary winding 11 varied from close-wound at the nose end to one-quarter inch at the opposite end. This would mean an average pitch slightly exceeding one-eighth inch which would Due to the configurations of the windings 11 and 12, they have opposed internal axial fields while their peripheral magnetic fields are made up of many closely spaced turn-to-turn field patterns like those-shown for the winding 11. This means that the peripheral magnetic field comprises many portions in which the flux is nearly normal to the surface of the casing 10. i

It is believed that the operation of the apparatus of FIG. 1 will be clearly understood from the foregoing introduction and description. Upon atmospheric reentry of a nose cone of the type illustrated, the forward end 10a of the nose cone produces intense ionization of the air which it encounters and this ionized air tends to form a plasma sheath extending and sweeping the walls of the casing 10. At the forward end of the nose cone, there is formed what is termed a bow shock wave which establishes a boundary 18 of the plasma separated from the point 10a. Upon closing the switch 9, the momentary surge of current through the windings 11 and 12 is effective substantially to dissipate the bow shock wave. Thereafter, the windings 11 and 12 cooperate to develop a peripheral magnetic field surrounding the casing 10 which is effective to repel or deflect the plasma sheath away from the walls of the casing 10, as illustrated, thus protecting them from excessive heating occurring upon deionization of the plasma were it to come in contact with the casing 10. By making the point 10a of a relatively readily vaporizable material such as aluminum, the formation of the plasma sheath at this point is facilitated so that the portion of the casing 10 immediatelybehind the point 10a is affected to a minimum extent. It will be understood that the point 10a is expendable and is made of such a mass that it will normally last for the period of atmospheric reentry.

While it has not been possible for applicant to prove out the invention on an actual space missile, it has been proven to operate and to accomplish its intended purpose upon a miniature missile nose cone under conditions of test closely simulating those encountered by a space missile in actual operation.

The essential design parameters of a miniature nose cone embodying an apparatus for establishing a plasma boundary surface in accordance with the invention were as follows:

Shell aluminum. Length 1 /4 inches. Outer diameter inch. Thickness inch. Nose end hemispherical. Winding 11 8 turns No. 20 gauge insulated copper wire. Diameter V2 inch, center-to-center. Pitch close-wound at nose end, increasing to inch at opposite end.

Winding 12 No. 40 gauge insulated copper wire. Pitch 40 turns per inch, uniform. Energizing current 2.5 amperes, 6 volts.

In proving out the invention, a number of shells were made to the foregoing specifications. In certain of these shells there were disposed apparatus for establishing a plasma boundary having the design parameters given above, while others of the shells, used as controls, were left empty. A plasma torch having a theoretical exhaust velocity of approximately 90 miles per second and a plasma temperature of approximately 15,000 C. was disposed at a distance of inch from the hemispherical end of the several shells successively. In such an arrangement, the actual velocity of the plasma at the forward end of the nose cone was of the order of 10 miles per second. The unmagnetized control shells were substantially completely vaporized in approximately 25 seconds. The shells including the apparatus described above operated as long as 33 minutes. Such a period of time would, of course, be far in excess of that required for a space missile to effect atmospheric reentry.

Referring now to FIG. 2 of the drawing, there is shown a modification of the apparatus of FIG. 1 effective to contain the high-temperature plasma formed by atomic fusion in a thermonuclear reactor. In this case, the primary helical winding 11' is wound with uniform pitch but, in other respects, may be similar to the winding 11 of FIG. 1. The secondary helical winding 12 may be wound on the winding 11' with such a pitch as to provide magnetic fields between adjacent turns of the winding 11 which are of an intensity of the same order as the intensity of the resultant axial component of the windings 11' and 12. At opposite ends of the apparatus are arranged magnetic apparatus 15 and 16, either of the permanent magnet or electromagnetic type, for developing axial magnetic fields opposing the axial component of the resultant magnetic field of the windings 11' and 12'. The assembly described will be supported in a suitable housing including conventional reactor elements, not shown. As a result, high-temperature plasma, indicated as lying within the dashed line boundary 17, is confined by the peripheral magnetic field of the winding 12' and by the axial magnetic fields of the devices 15 and 16, thus preventing the plasma 17 coming into contact with the walls of the reactor.

While there have been described What are, at present, considered to be the preferred embodiments of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein, without departing from the invention, and it is, therefore, aimed in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What is claimed is:

l. A space missile reentry cone comprising:

(a) a nonmangetic metallic casing;

(b) a plasma-deflecting apparatus disposed within said casing and including (c) a primary helical electrical winding;

(d) a secondary helical electrical winding wound on said primary windings. said windings extending substantially the length of said casing;

(e) and circuit means for supplying current continuously to both of said windings,

(f) the ampere-turns of said windings being proportioned to develop a peripheral magnetic field at least of the same order of intensity as their resultant axial field.

2. A space missile reentry cone comprising:

(a) a nonmangetic metallic casing;

(b) a plasma-deflecting apparatus disposed within said casing and including (c) a single-helix first electrical winding;

(cl) a double-helix second electrical winding coaxial with said first winding and connected in series therewith, said windings extending substantially the length of said casing;

(e) and circuit means for supplying current continuously to both of said windings;

(f) the ampere-turns of said windings being proportioned to develop a peripheral mangetic field at least of the same order of intensity as their resultant axial field.

3. A space missile reentry cone comprising:

(a) a nonmagnetic metallic casing;

(b) a plasma-deflecting apparatus disposed within said casing and including (c) a single-helix first electrical winding;

(d) a double-helix second electrical winding coaxial with said first winding, said windings extending substantially the length of said casing;

(e) and circuit means for supplying current continuously to both of said windings with such polarities that the axial components of their magnetic fields are opposed,

(f) the ampere-turns of said windings being proportioned to develop a peripheral magnetic field at least of the same order of intensity as their resultant axial field.

4. A space missille reentry cone comprising:

(a) a nonmagnetic metallic casing;

(b) a plasma-deflecting apparatus disposed within said casing and including (c) a single-helix first electrical winding;

((1) a double-helix second electrical winding coaxial with said first winding, said windings extending substantially the length of said casing;

(e) and circuit means for supplying current continuously to both of said windings,

(f) the ampere-turns of said windings being proportioned to develop a peripheral magnetic field at least of the same order of intensity as their resultant axial field.

5. A space missile reentry cone comprising:

(a) a nonmagnetic metallic casing having a forward end of reduced cross-section and of relatively readily vaporizable material;

(b) a plasma-deflecting apparatus disposed within said casing and including (c) a single-helix first electrical Winding;

(d) a double-helix second electrical winding coaxial with said first winding, said windings extending substantially the length of said casing;

(e) and circuit means for supplying current continuously to both of said windings,

(f) the ampere-turns of said windings being proportioned to develop a peripheral magnetic field at least of the same order of intensity as their resultant axial field.

6. A space missile reentry cone comprising:

(a) a nonmagnetic metallic casing having a needlepoint forward end of relatively readily vaporizable material;

(b) a plasma-deflecting apparatus disposed within said casing and including (o) a single-helix first electrical winding;

(d) a double-helix second electical winding coaxial with said first winding, said windings extending substantially the length of said casing;

(e) and circuit means for supplying current continuously to both of said windings,

(f) the ampere-turns of said windings being proportioned to develop a peripheral magnetic field at least 6 of the same order of intensity as their resultant axial field.

7. A space missile reentry cone comprising:

(a) a nonmagnetic metallic casing having a forward end of reduced cross-section and constructed of aluminum;

(b) a plasma-deflecting apparatus disposed within said casing and including (c) a single-helix first electrical winding;

(d) a double-helix second electrical winding coaxial with said first winding, said windings extending substantially the length of said casing;

(e) and circuit means for supplying current continuously to both of said windings,

(f) the ampere-turns of said windings being proportioned to develop a peripheral magnetic field at least of the same order of intensity as their resultant axial field.

8. A space missile reentry cone comprising:

(a) nonmagnetic metallic casing;

(b) a plasma-deflecting apparatus disposed within said casing and including (c) a single-helix first electrical winding having a pitch progressively decreasing toward the forward end of the cone;

(d) a double-helix second electrical winding coaxial with said first winding, said windings extending substantially the length of said casing;

(e) and circuit means for supplying current continu ously to both of said windings,

(f) the ampere-turns of said windings being pr0por tioned to develop a peripheral magnetic field at least of the same order of intensity as their resultant axial field.

References Cited by the Examiner UNITED STATES PATENTS 3,034,439 5/1962 Hirsch 102-92.5 3,093,078 6/1963 Ondrejka 10292.5 3,101,310 8/1963 Post 204-193 3,107,211 10/1963 Mallinckrodt 204l93 OTHER REFERENCES Kantrowitz: Introducing Magnetohydrodynamics, Astronautics, vol. 3, No. 10, October 1958, pp. l8-20 and 74-77.

NASA Tech. Note 3971, May 1957, pp. 43-46.

BENJAMIN A. BORCHELT, Primary Examiner.

FRED C. MATTERN, JR., Examiner. 

1. A SPACE MISSILE REENTRY CONE COMPRISING: (A) A NONMANGETIC METALLIC CASING; (B) A PLASMA-DEFLECTING APPARATUS DISPOSED WITHIN SAID CASING AND INCLUDING (C) A PRIMARY HELICAL ELECTRICAL WINDING; (D) A SECONDARY HELICAL ELECTRICAL WINDING WOUND ON SAID PRIMARY WINDINGS, SAID WINDINGS EXTENDING SUBSTANTIALLY THE LENGTH OF SAID CASING; (E) AND CIRCUIT MEANS FOR SUPPLYING CURRENT CONTINUOUSLY TO BOTH OF SAID WINDINGS, (F) THE AMPERE-TURNS OF SAID WINDINGS BEING PROPORTIONED TO DEVELOP A PERIPHERAL MAGNETIC FIELD AT LEAST OF THE SAME ORDER OF INTENSITY AS THEIR RESULTANT AXIAL FIELD. 